At present, a channel layer of an oxide thin film transistor (TFT) is formed by using an amorphous metal oxide semiconductor (MOS). The Oxide TFT mainly involves ZnO-based semiconductor TFT, e.g., Indium Gallium Zinc Oxide (IGZO) semiconductor, and has attracted considerable attentions from liquid crystal industries due to its excellent performances such as high mobility, low sub-threshold value, low leakage current, low temperature manufacturability, and so on. However, the channel layer of the Oxide TFT in existing technology still involves several problems to be solved.
In an existing technology, the channel layer of an Oxide TFT is usually deposited in an atmosphere of Ar gas and O2 gas, which may result in defects of valence state V[O]. Such defects will capture a large number of carriers, and finally lead to a phenomenon like hysteresis, which influences the switching characteristic of the Oxide TFT and thus the quality of a display panel.
FIG. 1 is a schematic view illustrating a structure of an Oxide TFT array substrate in the existing technology. As shown in FIG. 1, the Oxide TFT array substrate comprises a gate electrode 2, a gate insulating layer 3, a channel layer (also referred to as an active layer) 4, a barrier layer 5, a source electrode 6a, a drain electrode 6b, a passivation layer 7 and a pixel electrode 8, which are disposed on a substrate 1; the channel layer 4 is formed by using a metal oxide material such as IGZO. In the existing technology, generally, the source and the drain electrodes are prepared by using a metal or a metal oxide such as Al, Mo, Ti and Indium Oxide. The channel layer of such kind of Oxide TFT has a valence band with different energy level from that of metal, thereby generating a certain potential barrier, which influences the migration rate of carriers. Therefore, the electrical characteristic of the Oxide TFT is always affected by carriers in the channel layer, and an interface between the source electrode, the drain electrode and the channel layer has relatively larger contact resistance, so the hysteresis phenomenon is notable.